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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

GLACIERS OF HARRIMAN FIORD AND PORT WELLS          347
forest from Pt. Doran to Wedge Glacier and alder thickets extend to TTfl.rriTnn.Ti Glacier, contrasting with the western side which has alder thickets between Surprise Inlet and the head though only one very stunted spruce was seen.
The presence of thick forest nearly at sea level on Point Doran, with trees possibly over a century of age, shows that Barry Glacier has not overridden this point for at least 100 years, as Gilbert pointed out; and it seems probable that since it ceased to coalesce with Harriman Glacier, Barry Glacier has never reached Point Doran and dammed Haniman Fiord into a lake; for there are neither elevated shorelines nor deltas along its margins. Excepting in southern Harriman Fiord the forest is mature and vigorous, and there are fewer open glades in the coniferous forest of Harriman Fiord than near Columbia Glacier. The oldest tree whose age we determined was 22^ inches in diameter and had 225 annual rings. Muir, however, found one hemlock in 1899 * only nine inches in diameter which had attained 325 years. We found trees in Harriman Fiord in 1910 which judging by their diameters, must have been even older than that noted by Muir. Fernow observed in 18992 that logs in Prince William Sound showed the following relationships of diameter to age:
"50 annual rings, 11 inches 72        "         "   12 to 15 inches 80        "         "   20 inches 125        "         "   22 inches."
This vegetation proves clearly that these fiords have not been occupied by brimming ice streams since at least the sixteenth century. Gilbert stated in 1899 that "the condition of extreme glaciation . . . does not belong to the series of modern changes. - . . Were it of comparatively recent date the fiord would now be destitute of trees, but such is not the fact. It is true that the slopes are bare in the immediate vicinity of the glaciers, and that the valley walls enclosing the greater glaciers . . . support no trees, but the lower parts of the fiord walls are elsewhere covered by a hemlock forest.
As to the proper interpretation of the peculiarities of forest distribution the case is not altogether clear. In other localities there has seemed good reason to ascribe absence of forest to recent occupation by ice, but here there is a sort of transition from forest to barren which suggests climatic limitation. In the zone of transition the trees are not young and vigorous, as when invading newly-acquired territory, but scrawny and ill-favored, as though struggling desperately against the attack of hostile conditions. In an illustration, representing the edge of the forest nearest to Harriman Glacier, the rareness of branches on the side toward the water suggests that winter fogs driven landward overwhelm the boughs with loads of ice."
From this and from our own observations we are convinced that the presence or absence of trees and their size are not absolute criteria for use indiscriminately in interpreting glacial history where human records are lacking. That the rate of tree growth varies greatly under climatic, soil, and drainage conHitions in this region is shown by the great variations in the relation between diameter and number of annual rings already -quoted, and by the following record of a spruce found near Baker Glacier in 1910. The last ten years of growth were very rapid, as shown by the annual rings, the previous ten were very slow indeed, and the first 75 years were rapid. With evidence df decades of
1 Muir, John, Harriman Alaska Expedition, Vol. I,1002, p. 135.  Fernow, B. E., Harriman Alaska Expedition, Vol. n, 1902, p. 255.